Flexible shaft coupling

ABSTRACT

A flexible shaft coupling is of the kind comprising two annular assemblies which transmit torque between two rigid coupling parts which are arranged concentrically one within the other. The annular assemblies are concentric and have a space between them, and groups of radially directed filament loops or turns, which are embedded in an elastomeric mass, extend around members of the assemblies to interconnect the assemblies. Parts of the loops or turns between the members are supported on elastic cushions, which are formed by parts of the elastomeric masses, and are displaceable inwards into gaps between the members and within the elastomeric masses. The members of one assembly are attached to one coupling part and the members of the other assembly are attached to the other coupling parts. In order to ensure that in service, the filament loops or turns and the elastomeric masses in which they are embedded remain stressed in tension, in spite of fluctuations in the torque transmitted, the groups of filament loops or turns in their masses of elastomeric material are mounted so that they can pivot relative to the rigid coupling parts about axes which are parallel to the common axis of the coupling parts.

The invention refers to a flexible shaft coupling comprising two annularassemblies which transmit torque between two rigid coupling parts whichare arranged concentrically one within the other, the annular assembliesbeing concentric with a space between them, and groups of radiallydirected filament loops or turns embedded in an elastomeric mass, theloops or turns extending around members of the assemblies tointerconnect the assemblies, parts of the loops or turns between themembers being supported on elastic cushions which are displaceableinwards into gaps between the members and within the elastomeric masses,the members of one assembly being attached to one coupling part and themembers of the other assembly being attached to the other coupling part.

In one such coupling which is described in German Pat. No. 2,251,236certain disadvantages occur in service owing to the fact that when therigid coupling parts twist relative to each other, the filament loops orturns are not stressed over the whole of their peripheries in tensionbut are partially stressed, mainly in the regions where the loops passround the members, in compression and bending. Because of this, relativemovements occur between adjacent filaments and between the filaments andtheir surrounding elastomeric masses. These relative movements in turnlead after a fairly long working life to local separations between theseparts which are initially bonded together by vulcanisation. They alsolead to friction between the separated parts and hence to theundesirable development of heat as well as to premature wearing out ofthe flexible parts. These disadvantages become the more noticeable, thegreater the torque transmitted by the coupling and the more frequentlythe stresses on the flexible parts change.

The object of the present invention is to improve the couplings of thekind described above in such a way that the filament loops or turns andthe elastomeric masses are, during service of the coupling, as far aspossible loaded only in tension and hence all of the disadvantagesarising from other loadings are avoided or lessened.

To this end, according to this invention, in a flexible shaft couplingof the kind described above, the groups of filament loops or turns intheir masses of elastomeric material are mounted so that they can pivotrelative to the rigid coupling parts about axes which are parallel tothe common axis of the coupling parts.

Because of this mounting, the groups of loops or turns with the massesenveloping them are twisted as a whole relative to the coupling partsunder the influence of the torque being transmitted by the coupling andthe loops are thus aligned along the direction of tension, that is, theyare loaded still substantially only in tension. Changes in torque havethe effect only of producing oscillations in tension, whilst thependulum movements resulting from the change in torque act only upon thepivotal mountings which can be constructed to withstand the movementswithout undue wear or tear. Filament loops or turns mounted so that theycan pivot in the manner described, also yield considerably more easilyto alterations in the torque than can be done by filamentloop-reinforced elastomeric parts the ends of which are fixed immovablyin ring sectors connected rigidly to the rigid coupling parts. Couplingsin accordance with the invention can consequently easily display highinitial flexibility and a high degree of progressive resistance todeflection under torque. Because of this the couplings follow morerapidly the introduced and increased torque and the restoring forces ofthe previously elastically deformed elastomeric parts.

Further possibilities arising from the pivotal mounting of the filamentsand the elastomeric masses, of improvement in these parts in themselvesas well as in respect of their arrangement, operation and loading, andalso of the simplified production of the members of the assemblies willbe discussed in the description below of examples of couplings inaccordance with the invention.

Three examples of couplings in accordance with the invention will now bedescribed with reference to the accompanying drawings, in which:

FIG. 1 is an elevation looking in an axial direction of a right-angledsector of one example;

FIG. 2 is an elevation of two sector shaped members forming part of theexample of FIG. 1, with a filament winding connecting the members shownin section;

FIG. 3 is a section on an axially extending radial plane through onehalf of the coupling of FIGS. 1 and 2, as seen along the line II--II inFIG. 2;

FIG. 4 is a section similar to FIG. 3, but as seen along the lineIII--III in FIG. 2;

FIGS. 5a and 5b each show in elevation one half of each of two furtherexamples of couplings; and,

FIGS. 6a and 6b are axial sections through the couplings shown in FIGS.5a and 5b.

In the example shown in FIGS. 1 to 4 and as may be seen particularlyclearly from FIGS. 1 and 2, two members in the form of concentricsectors 1 and 2 bounded by the same axially extending radial plane andlying one radially within the other with a space between them, areconnected by two groups of filament loops or turns 5 of which in FIG. 2only one group is illustrated. The sectors 1 and 2 are provided, attheir circumferential edges with radially extending projections 1a, 2alying in the same radial planes. Faces 3 and 4 of these projectionssecure the groups 5 of filament loops against movement circumferentiallyof the sectors.

The sectors 1 and 2 are each provided with a bore 10 lying on a centralaxially extending radial plane. These bores are used for receivingbearings by which the sectors 1 and 2 are mounted so that they can swingabout axially parallel bearing bolts 11 extending from rigid couplingparts 8 and 9 of the coupling (FIG. 4). Spacer rings 13 ensure thenecessary spacing of the sectors 1 and 2 from the rigid coupling parts 8and 9.

As may be seen from FIGS. 3 and 4 the groups 5 of filaments togetherwith the parts of the sectors 1 and 2 enveloped by them are embedded ina rubber mass 6. The rubber mass 6 together with the annular gap 7between the sectors 1 and 2 forms a central cavity open at its ends.This serves for the ventilation and cooling of the rubber parts as wellas forming a space for the displacement of parts 6a of the rubber massincluded between the sectors 1 and 2 and the filament loops 5 which arearched axially outwards.

Instead of the simple mounting of the ring sectors 1 and 2, shown inFIGS. 1 to 4, the sectors may be supported on the ends of the bolts 11by sliding bearings and they may be secured against sliding off thebolts 11 by circlips 12. Alternatively roller bearings may be providedor as in the example of FIG. 6a the sectors may be supported byball-head bearings 14. Ball-head bearings or roller bearings made asswivel bearings facilitate the adaptation of the flexible coupling partsto alterations in length and angular adjustments between the shaftscoupled by the coupling and prevent transverse loadings of the flexiblecoupling parts in axial directions, which are otherwise thereby caused.

In the example illustrated in FIGS. 1 to 4, because of the radialarrangement of the flexible parts formed by the filaments 5 and rubbermasses 6, transverse loadings of these parts are largely but notcompletely avoided. When the coupling is in service slight transverseloadings still result from the tension which occurs if the flexibleparts get stretched and their filament loops get slightly twisted out oftheir normal position.

Even these small residual transverse loadings are avoided in theexamples of the coupling shown in FIGS. 5a and 5b of the drawings.

In the example shown in FIG. 5a the flexible coupling parts arrangedbetween rigid coupling parts 18, 19 consist of straight sectors 21 and22 and rubber parts 16 each reinforced by a group of loops connectingthe sectors. The straight sectors 21 and 22 allow the rubber parts aswell as the filaments of the two filament groups to be arranged parallelto planes extending through the centers of the sectors and henceparallel to one another.

Thus, when the coupling is in service, the rubber parts and the filamentloops embedded in them loaded exclusively in tension and the parts ofthe rubber masses (FIG. 3) which support the filament loops on the ringsectors are loaded merely in compression.

The straight ring sectors 21, 22 furthermore allow the filament loops tobe arranged in layers of equal width along the length of the sectors.The winding of the groups of loops is thereby considerably facilitated.Depending upon the diameter of the coupling and the magnitude of torqueto be transmitted, the straight sectors may be parts of polygonal flatrings of any number of sides.

Axial bores 15 or 20 through the outer rigid coupling rings 9 or 19 (seeFIGS. 3 and 5a respectively) are used for fastening these rings to asecond hub part (not shown).

A further simplification in the production and in the maintenance of theflexible coupling parts results if the groups of filament loops embeddedin their rubber masses are not suspended as in the example of FIG. 5a inpairs from sectors to which they are connected by vulcanising, but ifinstead each group of loops embedded in its rubber mass is mountedindividually and pivotally on sectors which are resistant to bending.These sectors are then connected rigidly to the rigid coupling parts andserve to support the groups of loops as well as for the receiving andtransmission of the torque.

Such an example is illustrated in FIGS. 5b and 6b. In this example,groups 26 of loops embedded in a rubber mass are recessed in groovesround the end faces and a surface part, flattened between the end faces,of part cylinders 23 which are guided by their complete surface parts toslide on cylindrical bearing surfaces of recesses 24 in the sectors 31and 32 of divided flat rings. The sectors 31 and 32 are fixed immovablyby means of bolts 25 to the rigid coupling parts 18 and 19 respectively.

Cylindrical bearing surfaces for the part cylinders 23 are formed, forsimplification of production and assembly, by the walls ofsemi-cylindrical recesses 24 in the adjacent ends of the sectors 31, 32.In these recesses which complete hollow cylinders, the part cylinders 23are secured against axial shifting by flanges 23a surrounding theirprojecting ends.

Where the groups 26 of loops are not connected in a vulcanisingoperation to the part cylinder 23 but are produced separately, thegroups of loops 26 are provided with internal projections 28 whichengage in recesses 29 in the surfaces of the part cylinder 23 which arecovered by them.

Since the end faces of the part cylinder 23 surrounded by the groups ofloops form only small areas against which the groups 26 of loops canbear through parts of a rubber mass enveloping them, the parts of eachgroup 26 of loops covering the annular gap 27 between the sectors 31 and32 are arched outwards towards one another by resilient bodies 30arranged between them and supported against one another.

The resilient bodies 30 preferably consist of elastomeric material andmay then be parts of the rubber mass enveloping the filament loops. Theymay alternatively be metal springs or combinations of springs, e.g.shock absorbers. The choice and the construction of the resilient bodies30 follows from the requirements which are imposed upon the line ofseparation at the coupling as well as upon the elasticity and upon thedamping value of the coupling.

Resilient bodies 30 may also be provided inside the rubber parts 16 ofloops as well as or instead of, cushions supporting these groups ofloops from the sectors 21, 22.

We claim:
 1. In a flexible shaft coupling comprising first and secondrigid coupling parts arranged concentrically one within the other abouta central axis, first and second annular assemblies, said annularassemblies being concentric with a space between them and each of saidannular assemblies including a plurality of members circumferentiallyspaced apart around the central axis, and transmission meansinterconnecting said members to transmit torque between said rigidcoupling parts, said transmission means including a plurality ofelastomeric masses and a plurality of groups of radially directedfilament loops, each of said groups being embedded in one of said massesand extending round one of said members in said first annular assemblyand round one of said members in said second annular assembly tointerconnect said assemblies, said loops including parts between saidmembers and elastic cushion means supporting said parts for displacementinwards into gaps between said members and within said elastomericmasses, the improvement comprising means pivotally mounting each of saidgroups and each of said masses of elastomeric material whereby saidgroups and said masses can pivot relative to said rigid coupling partsabout axes which are parallel to the central axis of said coupling partsand said pivot means comprises a plurality of groups of pivots, eachsaid group of pivots comprising a first pivot connected to said firstrigid coupling part and a second pivot connected to said second rigidcoupling part with said first and second pivots in each said group beingdisposed in radially spaced apart relation along a rectilinear lineextending radially outwardly from the central axis, and two of saidgroups of filament loops extend around each of said members, and saidfirst and second pivots pivotally connect each of said members to one ofsaid coupling parts for movement about an axis parallel to said centralaxis, and each of said members being in the form of a sector which iscircumferentially spaced from adjacent sectors in said annularassemblies.
 2. A shaft coupling as claimed in claim 1, in which each ofsaid members is in the form of a straight sector, said members of eachof said annular assemblies together forming a regular polygonal assemblyand said loops lying in planes parallel to axially extending radialplanes extending through the centres of said sectors.
 3. A shaftcoupling as claimed in claim 1, wherein said first and second pivotseach comprise a bearing, each of said bearings connecting one of saidmembers to one of said coupling parts, said bearings being adaptable foradjustments in the axial direction of said coupling parts.